[PATCH] fbdev: make pxafb more robust to errors with CONFIG_FB_PXA_PARAMETERS

pxafb.c runs into an oops if CONFIG_FB_PXA_PARAMETERS is enabled and no
parameters are set in command line.  The following patch avoids this
problem.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Cc: "Antonino A. Daplas" <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>